/**
  * 全局遮罩层
 */
.mask-layer {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.5);
    z-index: 999;
    opacity: 0;
    visibility: hidden;
    transition: opacity 0.3s ease;
}

.mask-layer--active {
    opacity: 1;
    visibility: visible;
}